The real question Dave is how much do you want and how do you intend to use it?

For instance if you only want 10-12mm, it's very easy to make from sheet and round it on a mandrel-no exotic tools or great skill required.

If you want more, one of us might be able to suggest an alternative.

That said, order it from abroad and you'll have it in ten days or so- no great problem either. Dennis.